[Patent Literature 1] JP 2005-316704 A
An in-vehicle system in a host vehicle is proposed to collect sounds outside of the host vehicle arriving from peripheral directions using microphones and reproduce sounds using speakers inside of the host vehicle as if arriving from the peripheral directions, in order to warn the driver of objects or events existing around the host vehicle; the objects or events include other vehicles including overtaking vehicles, pedestrians, and bicycles, for instance. For example, Patent Literature 1 describes a technology to determine a caution-needed direction, which the driver of a vehicle needs to pay attention to, based on behavior states such as the direction of the face of the driver, or operation states such as the state of the blinker of the vehicle, and then present peripheral sounds from the caution-needed direction with emphasis toward a vehicle interior of the vehicle.
However, the technology in Patent Literature 1 does not consider states outside the vehicle when determining the caution-needed direction; thus, the driver may not pay attention to the direction to which the driver needs to pay attention essentially.